Regex parsing of tags sucks. Setting $next to false doesn't work if you have any tags inside a pre/code/whatever. The current patch doesn't work with two nested pres. So, here are the stacks.

The stacks approach works for any number/kind of nested elements. It also keeps a dynamic list of the not texturizable tags and shortcodes, so that a plugin can modify them. This way you can opt-out your shortcode from wptexturize() (this fixes #6969).

Please, have a look at ​the unit tests, I would be happy if anybody adds more. They are really useful in this case.